The open source project first revealed its original Open Rack specification (version 0.5) back in December 2011. Now it has released the second version, dubbed v1.0 Open Rack specification.

Open Rack on track

The Open Compute Project described the new specifications as an evolution of the previous Open Rack specs. It said the new specifications offer an “exclusive focus on a single column rack design.”

This apparently allows for higher inlet temperature of 35°C, which “reflects other Open Compute designs and real-world data centre temperatures,” it said. The project also pointed out that the new specs allow for network switches to be deployed in various configurations, and “not just above the topmost power zone.”

The spec performs the seemingly earth-shattering feat of daring to change the fundamental unit of hardware. Instead of the traditional 19 inches, Open Compute units will be 21 inches, though they will still fit into the normal 24 inch wide racks in data centres.

Open compute uses a slightly taller height measurement. Instead of the traditional U unit, which is 44.75mm, it proposes that devices come in 48mm high increments, called the OpenU.

The new Open Rack standard allows for Compute chassis that are 10xOpenU high, and are supported on L-shaped brackets that directly snap into the vertical structural rack posts.

“These brackets, installable without tools, can be mounted at 0.5xOpenU (24mm) increments,” it said. Maximum height is reportedly dictated by the size of the power zone, but the project advises that heights above the suggested maximum of 2100mm “should be given closer scrutiny for stability.”

It also said innovative clips allows for the easy attachment of the chassis power connectors to the bus bars.

“The Open Rack is the first rack design to diverge from the existing 19 in rack standard, which had its origins in the railroad industry and was later adopted by the recording industry, among others,” the project said. “The 537mm width (about 21 inches) of the chassis has a lot of practical engineering benefits, like improved airflow, greater energy efficiency, and better volumetric efficiency, as there is more space used for IT equipment instead of just air and metal.”

The rack itself is 600mm wide, which makes it the same as the overall width of a 19” rack, so it fits into existing data centres worldwide.

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That data centre was considered at the time to be the most efficient in the world in terms of power consumption, using 38 percent less energy than the company’s other data centres while costing 24 percent less. The power usage effectiveness rating was 1.07, and only 7 percent of the power brought into the facility was used to cool down the facility.

The new Open Rack specs signal the likely future direction Facebook is going to take for its computing infrastructure, as it seeks more power efficiency and greener data centres. The social network giant has confirmed it has deployed the version 1.0 Open Rack spec for testing in its data centres.